On Starfleet vessels, and many others, the bridge is traditionally located on deck 1, or the top deck of the ship. It is from the bridge that many captains issues most of their commands. The bridge would typically give access to engineering, gravity control, damage control, environmental engineering, sciences and library computer, and security as well as helm control.
In the 23rd century there were some exceptions to the general rule that the bridge was on the top deck. On Walker-class starships of the mid-23rd century the bridge module was positioned at the bottom of the saucer section both in the prime and mirror universes. (DSC episodes: "The Vulcan Hello", "Despite Yourself")
On Starfleet vessels, the bridge is often a replaceable module. This increases the flexibility of the ship's performance and the useful lifespan of vessels. After the original bridge of the USS Yorktown was damaged, the bridge module of the USS Enterprise in service during the 2260s was used as a replacement for the Yorktown following its conversion into a museum ship and the Enterprise receiving a new module as part of its overall refit. (TNG novel: Crossover)
At the launch of the second Federation starship USS Enterprise in 2286, the bridge module resembled that of earlier refit Constitution-class vessels. Shortly after launch the module was replaced with a new module that contained a number of improvements over the earlier design.
During shakedown trials of the Galaxy-class USS Enterprise the regular bridge module was not yet ready for placement. A customized bridge module was placed on the ship, which could be ejected should the ship experience a critical systems failure. (TNG reference: Star Trek: The Next Generation Technical Manual) The regular bridge module that followed was used for the first seven years of the Enterprise-D's active service life until it was damaged in a Maquis attack, requiring its replacement. The new bridge module was similar to the previous bridge module except for the addition of additional consoles and an adjustment in the height of the command center. (TNG novel: Rogue Saucer, TNG movie: Generations)